In this specification it is to be understood that the natural sources of carotene include fruits, vegetables and other plant tissue, and animal tissue. A particularly important commercial source of carotene is certain types of algae.
Beta-carotene occurs in a number of different chemical isomer forms. Some of these are geometrical isomers which have a different orientation around one of the double bonds In the conjugated double bond structure of the molecule.
This can occur in a number of positions along the conjugated backbone to make a range of different geometrical isomers. In some cases there can even be more than one double bond where change of orientation occurs.
The most common geometrical isomer is the all trans isomer with a structure occurring as shown as follows where the main carbon chain of the molecule occurs in a trans (across) or straight configuration. ##STR1##
However, there are cis forms of beta-carotene which occur naturally, and can be produced by chemical synthesis, or formed by physical processes like heat on the all trans isomers, where the main carbon chain of the molecule takes a bend (cis) or sideways configuration. Naturally occurring cis forms of beta-carotene are not known to occur over a weight percentage of approximately 30% to less than 50% of the total carotenoid content.
Associated with the different geometric isomers are different properties and possible functions and for this reason there are potential benefits in relatively concentrated forms of the cis isomers.
In natural products such as fruit, vegetables, algae and other plant and animal material the carotenoids are stabilized as part of the cell structure in small micron or sub-micron sized particles in the cell organelles or even by association with other molecules which stabilize the isomeric forms produced by the biochemical pathways of the organism. However, in the preparation of concentrated forms of these materials for commercial products desired from the natural sources, the natural stabilising capacity of the cellular structure may be removed or reduced in the extraction and concentration of the carotenoids.
In addition, as the carotenoid products are concentrated to increase their beta-carotene concentrations and to remove the other cell material which is not desired in the product, there is a natural tendency for certain isomers to crystallize out.
Crystallisation is a problem in certain applications since the crystalline form may not be available for efficient use in the application because of its relative insolubility. Crystallisation occurs particularly with all trans beta-carotene and as a result it is not, for example, readily available for biological use.
Cis isomers, on the other hand are much less likely to crystallise and as a consequence are much more soluble than the trans isomers. For this reason, it is often more desirable to use beta-carotene containing compositions with higher concentrations of cis isomers for various applications. For example, the 9 cis isomer is much more readily soluble in oils than the all trans form. In fact, it is very difficult to get the 9 cis isomer to crystallize out from naturally derived oils, thus making it difficult or expensive to purify on a large scale.
Unlike trans isomers, cis isomers have a number of applications, including use in water dispersible food colourants and in tabletting powders. The cis isomers are also useful in a water dispersible form as emulsions for colouring and in beverages. They can also be used in special vitamin supplements in concentrates for direct supplementation or as part of food.
In naturally occurring products the proportion of cis isomers is rather small, but one of the highest proportions occurs in the halophillic alga Dunaliella salina where normally 30% to below 50% of the total carotenoid content occurs as the 9 cis form.
The present invention is accordingly directed to compositions with a high cis beta-carotene composition derived from natural sources.